Recently, there has been increasing interest in alternative energy due to the exhaustion of fossil fuels and the problems associated with environmental contamination. In particular, there has been great interest in a fuel cell that generates electricity using a reaction between oxygen and hydrogen as an alternative energy source because it is easy to obtain the raw materials for the reaction and the reaction causes little environmental contamination.
A fuel cell, which is a kind of electricity generator that converts the chemical energy of fuel into electrical energy through an electrochemical reaction in a fuel cell stack without changing the chemical energy of the fuel into heat by burning the fuel, can be used not only for supplying power for industry, homes, and vehicles, but also for supplying power for small-sized electrical/electronic products, particularly mobile devices.
As an example of a fuel cell, a polymer electrolyte membrane fuel cell that is generally used as a power supplier for driving vehicles includes: a membrane-electrode assembly that is composed of an electrolyte membrane, through which hydrogen ions move, and catalytic electrodes in which an electrochemical reaction is generated and which are attached to both sides of the electrolyte membrane; a gas diffusion layer that uniformly distributes the reaction gases and transmits generated electrical energy; a gasket and fasteners that maintain airtightness and appropriate pressure against reaction gases and cooling water; and a separator in which the reaction gases and the cooling water move.
Hydrogen, as the fuel, and air, as the oxidizer in a fuel cell, are supplied to the anode and the cathode of a membrane-electrode assembly, respectively, through channels in a separator, that is, the hydrogen is supplied to the anode and the air is supplied to the cathode. The hydrogen supplied to the anode is decomposed into hydrogen ions and electrons by a catalyst in the electrode layers on both sides of the electrolyte membrane, in which only the hydrogen ions are selectively transmitted to the cathode through the electrolyte membrane, which is a cation exchange membrane, and the electrons are transmitted to the cathode through the gas diffusion layer and the separator that are conductors.
At the cathode, the hydrogen ions supplied through the electrolyte membrane and the electrons transmitted through the separator cause a reaction that produces water with the oxygen in the air supplied to the cathode by an air supplier. In this process, the electrons flow through an external wire due to the movement of hydrogen ions, and this flow of electrons is current.
Accordingly, separators generally have a structure in which lands where the separator and the gas diffusion layer are in contact and channels that function as paths for the flow of fluids (including a reaction gas and cooling water) are repeatedly curved, so the channel at a side facing the gas diffusion layer is used as a space where a reaction gas such as hydrogen or air flows and the opposite channel is used as a space where cooling water flows. Therefore, the separator is composed of a total of two separators, that is, one separator having the hydrogen/cooling water channel and one separator having the air/cooling water channel.
The description provided above as a related art of the present disclosure is just for helping understanding the background of the present disclosure and should not be construed as being included in the related art known by those skilled in the art.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.